Abstract
The neuronal ceroid lipofuscinoses (NCL) are a group of inherited, severe neurodegenerative disorders also known as Batten disease. Juvenile NCL (JNCL) is caused by recessive loss-of-function mutations in CLN3, which encodes a transmembrane protein that regulates endocytic pathway trafficking, though its primary function is not yet known. The social amoeba Dictyostelium discoideum is increasingly utilized for neurological disease research and is particularly suited for investigation of protein function in trafficking. Therefore, here we establish new overexpression and knockout Dictyostelium cell lines for JNCL research. Dictyostelium Cln3 fused to GFP localized to the contractile vacuole system and to compartments of the endocytic pathway. cln3− cells displayed increased rates of proliferation and an associated reduction in the extracellular levels and cleavage of the autocrine proliferation repressor, AprA. Mid- and late development of cln3− cells was precocious and cln3− slugs displayed increased migration. Expression of either Dictyostelium Cln3 or human CLN3 in cln3− cells suppressed the precocious development and aberrant slug migration, which were also suppressed by calcium chelation. Taken together, our results show that Cln3 is a pleiotropic protein that negatively regulates proliferation and development in Dictyostelium. This new model system, which allows for the study of Cln3 function in both single cells and a multicellular organism, together with the observation that expression of human CLN3 restores abnormalities in Dictyostelium cln3− cells, strongly supports the use of this new model for JNCL research.
Highlights
The neuronal ceroid lipofuscinoses (NCL) are a group of inherited, severe neurodegenerative disorders known as Batten disease [1]
In an attempt to gain further insight into the possible mechanisms by which Cln3 deficiency leads to enhanced proliferation, we investigated two secreted proteins that modulate growth in Dictyostelium by repressing cell proliferation: autocrine proliferation repressor A (AprA) and counting factorassociated protein D (CfaD) [41,42]
We have shown that Dictyostelium contains an ortholog of CLN3, for which loss-of-function mutations in humans causes the childhood onset neurodegenerative disorder Juvenile NCL (JNCL)
Summary
The neuronal ceroid lipofuscinoses (NCL) are a group of inherited, severe neurodegenerative disorders known as Batten disease [1]. NCL disorders characteristically display aberrant lysosomal function and an excessive accumulation of lipofuscin in neurons and other cell types [2,3]. Clinical manifestations include vision loss, seizures, the progressive loss of motor function and psychological ability, and a reduced lifespan [4]. North American and Northern European populations have the highest rates of incidence, the NCL disorders have a worldwide distribution with varying incidence rates depending on the region (1:14000 to 1:100000) [9]. There are no effective treatments or cure for NCL disorders
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